Fischer-Tropsch (F-T) reactions, i.e., catalytic reactions for the production of C.sub.5 + liquid hydrocarbons from mixtures of hydrogen and carbon monoxide, are well known. The F-T process has become the subject of intense study for commercial development. The catalysts used in conducting F-T reactions are typically constituted of an Iron Group metal (Periodic Table of the Elements, Sargent-Welch Scientific Company, Copyright 1979) of Group VIII, e.g., iron, nickel or cobalt, distributed on a particulate refractory inorganic oxide support, e.g., titania. In formation of the catalyst, the catalytic properties of the Iron Group metal may be modified or promoted by an additional metal, or metals, from Group VIIB or VIII, e.g., platinum or rhenium.
In conducting an F-T synthesis reaction, a synthesis gas constituting a mixture of hydrogen and carbon monoxide is reacted over an Iron Group metal catalyst, e.g., Co--Re/TiO.sub.2, to produce a C.sub.5 + waxy hydrocarbon product which is separated into various fractions for further processing into transportation fuels, distillates, diesel and jet fuels, solvents and lubricating oils. While the waxy products from the F-T reactor are generally referred to as essentially "non-sulfur" containing compounds, the presence of sulfur in even a few parts, per million parts by weight (wppm) of a product, has been found to cumulatively poison a cobalt-containing catalyst and shorten its life. It thus becomes necessary for the viability of the process to periodically reactivate, or regenerate the sulfur deactivated catalyst.
Where the reaction product mixture in contact with the catalyst contains even a small amount of sulfur, the catalyst is cumulatively poisoned by the deposited sulfur. The result: All too soon the catalyst must be reactivated, or regenerated, by removal of the sulfur. Whereas methods are known for reactivating cobalt catalysts, such techniques often result in the removal of cobalt along with the sulfur. The result: All too soon the catalyst must be reworked, and replaced.
In U.S. Pat. No. 3,661,798, which issued May 9, 1972 to Institut Francais du Petrole, e.g., there is described a method wherein a sulfur-deactivated cobalt/silica catalyst is regenerated by the successive steps of heating the deactivated catalyst with a gas containing molecular oxygen at 300 to 600.degree. C., contacting the cooled catalyst with water at about 0 to 250.degree. C., and then with hydrogen at about 200 to 500.degree. C. The regeneration is not successfully reactivated when the carrier component of the catalyst is alumina. Moreover, it has been found that cobalt is extracted and lost from the catalyst even when the carrier component for the cobalt is silica. Accordingly, there remains a need for better methods, or processes for reactivating, or regenerating cobalt-containing catalysts.